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href="/frontend/js%E5%9F%BA%E7%A1%80/%E4%BB%BB%E5%8A%A1%E7%AE%A1%E7%90%86.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>任务管理</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E5%87%BD%E6%95%B0%E8%BF%9B%E9%98%B6.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>函数进阶</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E5%8E%9F%E5%9E%8B%E4%B8%8E%E7%BB%A7%E6%89%BF.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>原型与继承</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E5%9F%BA%E6%9C%AC%E7%B1%BB%E5%9E%8B.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>基本类型</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E5%AF%B9%E8%B1%A1.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>对象</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E5%B8%B8%E7%94%A8%E6%8A%80%E5%B7%A7.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>常用技巧</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E6%95%B0%E7%BB%84%E7%B1%BB%E5%9E%8B.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>数组类型</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E6%A8%A1%E5%9D%97%E8%AE%BE%E8%AE%A1.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>模块设计</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E6%AD%A3%E5%88%99%E8%A1%A8%E8%BE%BE%E5%BC%8F.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>正则表达式</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E7%A9%BA%E9%97%B4%E5%9D%90%E6%A0%87.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>空间坐标</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E7%B1%BB.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>类</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b7550ba0 data-v-b7550ba0><div class="item" data-v-b7550ba0><div class="indicator" data-v-b7550ba0></div><a class="VPLink link link" href="/frontend/js%E5%9F%BA%E7%A1%80/%E8%BF%AD%E4%BB%A3%E5%99%A8.html" data-v-b7550ba0><!--[--><p class="text" data-v-b7550ba0>迭代器</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><!--]--><!--[--><!--]--></nav></aside><div class="VPContent has-sidebar" id="VPContent" data-v-5d98c3a5 data-v-1428d186><div class="VPDoc has-sidebar has-aside" data-v-1428d186 data-v-39a288b8><!--[--><!--]--><div class="container" data-v-39a288b8><div class="aside" data-v-39a288b8><div class="aside-curtain" data-v-39a288b8></div><div class="aside-container" data-v-39a288b8><div class="aside-content" data-v-39a288b8><div class="VPDocAside" data-v-39a288b8 data-v-3f215769><!--[--><!--]--><!--[--><!--]--><nav aria-labelledby="doc-outline-aria-label" class="VPDocAsideOutline" data-v-3f215769 data-v-a5bbad30><div class="content" data-v-a5bbad30><div class="outline-marker" data-v-a5bbad30></div><div aria-level="2" class="outline-title" id="doc-outline-aria-label" role="heading" data-v-a5bbad30>目录</div><ul class="VPDocOutlineItem root" data-v-a5bbad30 data-v-b933a997><!--[--><!--]--></ul></div></nav><!--[--><!--]--><div class="spacer" data-v-3f215769></div><!--[--><!--]--><!----><!--[--><!--]--><!--[--><!--]--></div></div></div></div><div class="content" data-v-39a288b8><div class="content-container" data-v-39a288b8><!--[--><!--]--><main class="main" data-v-39a288b8><div style="position:relative;" class="vp-doc _frontend_js%E5%9F%BA%E7%A1%80_%E8%BF%AD%E4%BB%A3%E5%99%A8" data-v-39a288b8><div><h1 id="迭代器" tabindex="-1">迭代器 <a class="header-anchor" href="#迭代器" aria-label="Permalink to &quot;迭代器&quot;">​</a></h1><h2 id="遍历器" tabindex="-1">遍历器 <a class="header-anchor" href="#遍历器" aria-label="Permalink to &quot;遍历器&quot;">​</a></h2><p>现在很多语言中都存在 Iterator 遍历器（迭代器），目的是为了是用统一接口处理不同数据类型。在 JS 中包括 <code>Array/Object/Set/Map</code> 等多种集合数据结构，迭代器就是为了采用统一的方式遍历数据。</p><p>常用的解构与扩展运算符内部也在使用遍历器实现。</p><h2 id="解决的问题" tabindex="-1">解决的问题 <a class="header-anchor" href="#解决的问题" aria-label="Permalink to &quot;解决的问题&quot;">​</a></h2><p>以往遍历数据时比如使用 <code>for</code> 需要变量来记录每次迭代数据的位置，如果遍历多层需要设置多个变量用于记录并不方便。</p><h2 id="原始实现" tabindex="-1">原始实现 <a class="header-anchor" href="#原始实现" aria-label="Permalink to &quot;原始实现&quot;">​</a></h2><p>下面使用以往掌握的知识实现生成器，有助于更好的理解生成器。</p><div class="language-javascript line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">javascript</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#C678DD;">function</span><span style="color:#61AFEF;"> generator</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;font-style:italic;">arr</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#C678DD;">  let</span><span style="color:#E06C75;"> i</span><span style="color:#56B6C2;"> =</span><span style="color:#D19A66;"> 0</span><span style="color:#ABB2BF;">;</span></span>
<span class="line"><span style="color:#C678DD;">  return</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#61AFEF;">    next</span><span style="color:#ABB2BF;">() {</span></span>
<span class="line"><span style="color:#C678DD;">      let</span><span style="color:#E06C75;"> done</span><span style="color:#56B6C2;"> =</span><span style="color:#E5C07B;"> arr</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">length</span><span style="color:#56B6C2;"> &lt;=</span><span style="color:#E06C75;"> i</span><span style="color:#ABB2BF;">;</span></span>
<span class="line"><span style="color:#C678DD;">      return</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#E06C75;">        value</span><span style="color:#ABB2BF;">: </span><span style="color:#E06C75;">done</span><span style="color:#C678DD;"> ?</span><span style="color:#D19A66;"> undefined</span><span style="color:#C678DD;"> :</span><span style="color:#E06C75;"> arr</span><span style="color:#ABB2BF;">[</span><span style="color:#E06C75;">i</span><span style="color:#56B6C2;">++</span><span style="color:#ABB2BF;">],</span></span>
<span class="line"><span style="color:#E06C75;">        done</span><span style="color:#ABB2BF;">: </span><span style="color:#E06C75;">done</span></span>
<span class="line"><span style="color:#ABB2BF;">      };</span></span>
<span class="line"><span style="color:#ABB2BF;">    }</span></span>
<span class="line"><span style="color:#ABB2BF;">  };</span></span>
<span class="line"><span style="color:#ABB2BF;">}</span></span>
<span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> gen</span><span style="color:#56B6C2;"> =</span><span style="color:#C678DD;"> new</span><span style="color:#61AFEF;"> generator</span><span style="color:#ABB2BF;">([</span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">3</span><span style="color:#ABB2BF;">]);</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E5C07B;">gen</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">next</span><span style="color:#ABB2BF;">()); </span><span style="color:#7F848E;font-style:italic;">//{value: 1, done: false}</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E5C07B;">gen</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">next</span><span style="color:#ABB2BF;">()); </span><span style="color:#7F848E;font-style:italic;">//{value: 2, done: false}</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E5C07B;">gen</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">next</span><span style="color:#ABB2BF;">()); </span><span style="color:#7F848E;font-style:italic;">//{value: 3, done: false}</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E5C07B;">gen</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">next</span><span style="color:#ABB2BF;">()); </span><span style="color:#7F848E;font-style:italic;">//{value: undefined, done: false}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br></div></div><h2 id="原理分析" tabindex="-1">原理分析 <a class="header-anchor" href="#原理分析" aria-label="Permalink to &quot;原理分析&quot;">​</a></h2><p>默认情况下对象是不可以迭代的，当添加<code>[Symbol.iterator]</code>生成器后，就会变为可迭代对象。</p><div class="language-javascript line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">javascript</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> object</span><span style="color:#56B6C2;"> =</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#E06C75;">  data</span><span style="color:#ABB2BF;">: [],</span></span>
<span class="line"><span style="color:#C678DD;">  *</span><span style="color:#ABB2BF;">[</span><span style="color:#E5C07B;">Symbol</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">]() {</span></span>
<span class="line"><span style="color:#C678DD;">    for</span><span style="color:#ABB2BF;"> (</span><span style="color:#C678DD;">const</span><span style="color:#E5C07B;"> iterator</span><span style="color:#C678DD;"> of</span><span style="color:#E5C07B;"> this</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">data</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#C678DD;">      yield</span><span style="color:#E06C75;"> iterator</span><span style="color:#ABB2BF;">;</span></span>
<span class="line"><span style="color:#ABB2BF;">    }</span></span>
<span class="line"><span style="color:#ABB2BF;">  },</span></span>
<span class="line"><span style="color:#61AFEF;">  push</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;font-style:italic;">item</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#E5C07B;">    this</span><span style="color:#ABB2BF;">.</span><span style="color:#E5C07B;">data</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">push</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;">item</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#ABB2BF;">  }</span></span>
<span class="line"><span style="color:#ABB2BF;">};</span></span>
<span class="line"><span style="color:#E5C07B;">object</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">push</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&quot;2&quot;</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#E5C07B;">object</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">push</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&quot;1&quot;</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#C678DD;">for</span><span style="color:#ABB2BF;"> (</span><span style="color:#C678DD;">const</span><span style="color:#E5C07B;"> iterator</span><span style="color:#C678DD;"> of</span><span style="color:#E06C75;"> object</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#E5C07B;">  console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#ABB2BF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><p>数据结构本身或在原型链上包含 <code>Symbol.iterator</code> 遍历器生成方法时即为可迭代对象。<code>Symbol.iterator</code> 返回<code>next</code> 方法。</p><div class="language-javascript line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">javascript</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> obj</span><span style="color:#56B6C2;"> =</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#E06C75;">  data</span><span style="color:#ABB2BF;">: [</span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">3</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">4</span><span style="color:#ABB2BF;">],</span></span>
<span class="line"><span style="color:#E06C75;">  pos</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">,</span></span>
<span class="line"><span style="color:#ABB2BF;">  [</span><span style="color:#E5C07B;">Symbol</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">]() {</span></span>
<span class="line"><span style="color:#E06C75;">    self</span><span style="color:#56B6C2;"> =</span><span style="color:#E5C07B;"> this</span><span style="color:#ABB2BF;">;</span></span>
<span class="line"><span style="color:#C678DD;">    return</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#61AFEF;">      next</span><span style="color:#ABB2BF;">() {</span></span>
<span class="line"><span style="color:#C678DD;">        let</span><span style="color:#E06C75;"> value</span><span style="color:#56B6C2;"> =</span><span style="color:#E5C07B;"> self</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">data</span><span style="color:#ABB2BF;">[</span><span style="color:#E5C07B;">self</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">pos</span><span style="color:#ABB2BF;">];</span></span>
<span class="line"><span style="color:#C678DD;">        let</span><span style="color:#E06C75;"> done</span><span style="color:#56B6C2;"> =</span><span style="color:#56B6C2;"> ++</span><span style="color:#E5C07B;">self</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">pos</span><span style="color:#56B6C2;"> &gt;</span><span style="color:#E5C07B;"> self</span><span style="color:#ABB2BF;">.</span><span style="color:#E5C07B;">data</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">length</span><span style="color:#ABB2BF;">;</span></span>
<span class="line"><span style="color:#C678DD;">        return</span><span style="color:#ABB2BF;"> { </span><span style="color:#E06C75;">value</span><span style="color:#ABB2BF;">, </span><span style="color:#E06C75;">done</span><span style="color:#ABB2BF;"> };</span></span>
<span class="line"><span style="color:#ABB2BF;">      }</span></span>
<span class="line"><span style="color:#ABB2BF;">    };</span></span>
<span class="line"><span style="color:#ABB2BF;">  }</span></span>
<span class="line"><span style="color:#ABB2BF;">};</span></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">// let iterator = obj[Symbol.iterator]();</span></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">// console.log(iterator.next());</span></span>
<span class="line"><span style="color:#C678DD;">for</span><span style="color:#ABB2BF;"> (</span><span style="color:#C678DD;">const</span><span style="color:#E5C07B;"> iterator</span><span style="color:#C678DD;"> of</span><span style="color:#E06C75;"> obj</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#E5C07B;">  console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#ABB2BF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br></div></div><p>如果对象是数字键并包含<code>length</code>可以直接引用数组迭代器</p><div class="language-javascript line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">javascript</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> object</span><span style="color:#56B6C2;"> =</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#D19A66;">  0</span><span style="color:#ABB2BF;">: </span><span style="color:#98C379;">&quot;1&quot;</span><span style="color:#ABB2BF;">,</span></span>
<span class="line"><span style="color:#D19A66;">  1</span><span style="color:#ABB2BF;">: </span><span style="color:#98C379;">&quot;2&quot;</span><span style="color:#ABB2BF;">,</span></span>
<span class="line"><span style="color:#D19A66;">  2</span><span style="color:#ABB2BF;">: </span><span style="color:#98C379;">&quot;3&quot;</span><span style="color:#ABB2BF;">,</span></span>
<span class="line"><span style="color:#E06C75;">  length</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">3</span><span style="color:#ABB2BF;">,</span></span>
<span class="line"><span style="color:#ABB2BF;">  [</span><span style="color:#E5C07B;">Symbol</span><span style="color:#E06C75;">.iterator</span><span style="color:#ABB2BF;">]: </span><span style="color:#E5C07B;">Array</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">prototype</span><span style="color:#ABB2BF;">[</span><span style="color:#E5C07B;">Symbol</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">]</span></span>
<span class="line"><span style="color:#ABB2BF;">};</span></span>
<span class="line"><span style="color:#C678DD;">for</span><span style="color:#ABB2BF;"> (</span><span style="color:#C678DD;">const</span><span style="color:#E5C07B;"> iterator</span><span style="color:#C678DD;"> of</span><span style="color:#E06C75;"> object</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#E5C07B;">  console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#ABB2BF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><p>带终止的迭代器</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#7F848E;font-style:italic;">// 案例: 创建一个教室类, 创建出来的对象都是可迭代对象</span></span>
<span class="line"><span style="color:#C678DD;">class</span><span style="color:#E5C07B;"> Classroom</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#C678DD;">  constructor</span><span style="color:#ABB2BF;">( </span><span style="color:#E06C75;font-style:italic;">students</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#E5C07B;">    this</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">students</span><span style="color:#56B6C2;"> =</span><span style="color:#E06C75;"> students</span></span>
<span class="line"><span style="color:#ABB2BF;">  }</span></span>
<span class="line"><span style="color:#61AFEF;">  entry</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;font-style:italic;">newStudent</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#E5C07B;">    this</span><span style="color:#ABB2BF;">.</span><span style="color:#E5C07B;">students</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">push</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;">newStudent</span><span style="color:#ABB2BF;">)</span></span>
<span class="line"><span style="color:#ABB2BF;">  }</span></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">  // 实现迭代器</span></span>
<span class="line"><span style="color:#ABB2BF;">  [</span><span style="color:#E5C07B;">Symbol</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">]() {</span></span>
<span class="line"><span style="color:#C678DD;">    let</span><span style="color:#E06C75;"> index</span><span style="color:#56B6C2;"> =</span><span style="color:#D19A66;"> 0</span></span>
<span class="line"><span style="color:#C678DD;">    return</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#61AFEF;">      next</span><span style="color:#ABB2BF;">: () </span><span style="color:#C678DD;">=&gt;</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#C678DD;">        if</span><span style="color:#ABB2BF;"> (</span><span style="color:#E06C75;">index</span><span style="color:#56B6C2;"> &lt;</span><span style="color:#E5C07B;"> this</span><span style="color:#ABB2BF;">.</span><span style="color:#E5C07B;">students</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">length</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#C678DD;">          return</span><span style="color:#ABB2BF;"> { </span><span style="color:#E06C75;">done</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">false</span><span style="color:#ABB2BF;">, </span><span style="color:#E06C75;">value</span><span style="color:#ABB2BF;">: </span><span style="color:#E5C07B;">this</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">students</span><span style="color:#ABB2BF;">[</span><span style="color:#E06C75;">index</span><span style="color:#56B6C2;">++</span><span style="color:#ABB2BF;">] }</span></span>
<span class="line"><span style="color:#ABB2BF;">        } </span><span style="color:#C678DD;">else</span><span style="color:#ABB2BF;"> {</span></span>
<span class="line"><span style="color:#C678DD;">          return</span><span style="color:#ABB2BF;"> { </span><span style="color:#E06C75;">done</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">true</span><span style="color:#ABB2BF;">, </span><span style="color:#E06C75;">value</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">undefined</span><span style="color:#ABB2BF;"> }</span></span>
<span class="line"><span style="color:#ABB2BF;">        }</span></span>
<span class="line"><span style="color:#ABB2BF;">      },</span></span>
<span class="line"><span style="color:#61AFEF;">      return</span><span style="color:#ABB2BF;">: () </span><span style="color:#C678DD;">=&gt;</span><span style="color:#ABB2BF;"> {    </span><span style="color:#7F848E;font-style:italic;">//监听迭代器停止</span></span>
<span class="line"><span style="color:#E5C07B;">        console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&quot;迭代器提前终止了~&quot;</span><span style="color:#ABB2BF;">)</span></span>
<span class="line"><span style="color:#C678DD;">        return</span><span style="color:#ABB2BF;"> { </span><span style="color:#E06C75;">done</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">true</span><span style="color:#ABB2BF;">, </span><span style="color:#E06C75;">value</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">undefined</span><span style="color:#ABB2BF;"> }</span></span>
<span class="line"><span style="color:#ABB2BF;">      }</span></span>
<span class="line"><span style="color:#ABB2BF;">    }</span></span>
<span class="line"><span style="color:#ABB2BF;">  }</span></span>
<span class="line"><span style="color:#ABB2BF;">}</span></span>
<span class="line"><span style="color:#ABB2BF;"> </span></span>
<span class="line"><span style="color:#C678DD;">const</span><span style="color:#E5C07B;"> classroom</span><span style="color:#56B6C2;"> =</span><span style="color:#C678DD;"> new</span><span style="color:#61AFEF;"> Classroom</span><span style="color:#ABB2BF;">( [</span><span style="color:#98C379;">&quot;学生1&quot;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&quot;学生2&quot;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&quot;学生3&quot;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&quot;学生4&quot;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&quot;学生5&quot;</span><span style="color:#ABB2BF;">])</span></span>
<span class="line"><span style="color:#E5C07B;">classroom</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">entry</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&quot;lilei&quot;</span><span style="color:#ABB2BF;">)</span></span>
<span class="line"><span style="color:#ABB2BF;"> </span></span>
<span class="line"><span style="color:#C678DD;">for</span><span style="color:#ABB2BF;"> (</span><span style="color:#C678DD;">const</span><span style="color:#E5C07B;"> stu</span><span style="color:#C678DD;"> of</span><span style="color:#E06C75;"> classroom</span><span style="color:#ABB2BF;">) {</span></span>
<span class="line"><span style="color:#E5C07B;">  console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;">stu</span><span style="color:#ABB2BF;">)</span></span>
<span class="line"><span style="color:#C678DD;">  if</span><span style="color:#ABB2BF;"> (</span><span style="color:#E06C75;">stu</span><span style="color:#56B6C2;"> ===</span><span style="color:#98C379;"> &quot;学生4&quot;</span><span style="color:#ABB2BF;">) </span><span style="color:#C678DD;">break</span></span>
<span class="line"><span style="color:#ABB2BF;">}</span></span>
<span class="line"><span style="color:#ABB2BF;"> </span></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">// 打印</span></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">  // 学生1</span></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">  // 学生2</span></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">  // 学生3</span></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">  // 学生4</span></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">  // 迭代器提前终止了~</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br><span class="line-number">31</span><br><span class="line-number">32</span><br><span class="line-number">33</span><br><span class="line-number">34</span><br><span class="line-number">35</span><br><span class="line-number">36</span><br><span class="line-number">37</span><br><span class="line-number">38</span><br><span class="line-number">39</span><br><span class="line-number">40</span><br><span class="line-number">41</span><br></div></div><p>系统内置的 <code>Array/Set/String/Map/NodeList</code> 对象都已经内置了迭代器，下面是体验数组迭代器的使用。</p><div class="language-javascript line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">javascript</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> arr</span><span style="color:#56B6C2;"> =</span><span style="color:#ABB2BF;"> [</span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&quot;4&quot;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&quot;6&quot;</span><span style="color:#ABB2BF;">];</span></span>
<span class="line"><span style="color:#C678DD;">const</span><span style="color:#E5C07B;"> iterator</span><span style="color:#56B6C2;"> =</span><span style="color:#E06C75;"> arr</span><span style="color:#ABB2BF;">[</span><span style="color:#E5C07B;">Symbol</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">]();</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E5C07B;">iterator</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">next</span><span style="color:#ABB2BF;">());</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>字符串同样实现了遍历器</p><div class="language-javascript line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">javascript</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> hd</span><span style="color:#56B6C2;"> =</span><span style="color:#98C379;"> &quot;love&quot;</span><span style="color:#ABB2BF;">;</span></span>
<span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> iterator</span><span style="color:#56B6C2;"> =</span><span style="color:#E06C75;"> hd</span><span style="color:#ABB2BF;">[</span><span style="color:#E5C07B;">Symbol</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">]();</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E5C07B;">iterator</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">next</span><span style="color:#ABB2BF;">());</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E5C07B;">iterator</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">next</span><span style="color:#ABB2BF;">());</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><p>再来看看 set 类型同样实现了遍历器</p><div class="language-javascript line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">javascript</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> hd</span><span style="color:#56B6C2;"> =</span><span style="color:#C678DD;"> new</span><span style="color:#61AFEF;"> Set</span><span style="color:#ABB2BF;">().</span><span style="color:#61AFEF;">add</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&quot;2&quot;</span><span style="color:#ABB2BF;">).</span><span style="color:#61AFEF;">add</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&quot;3&quot;</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> f</span><span style="color:#56B6C2;"> =</span><span style="color:#E06C75;"> hd</span><span style="color:#ABB2BF;">[</span><span style="color:#E5C07B;">Symbol</span><span style="color:#ABB2BF;">.</span><span style="color:#E06C75;">iterator</span><span style="color:#ABB2BF;">]();</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E5C07B;">f</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">next</span><span style="color:#ABB2BF;">());</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><h2 id="解构与扩展" tabindex="-1">解构与扩展 <a class="header-anchor" href="#解构与扩展" aria-label="Permalink to &quot;解构与扩展&quot;">​</a></h2><p>常用的解构与扩展运算符内部也在使用遍历器实现。</p><p>数组扩展调用遍历器</p><div class="language-javascript line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">javascript</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> arr</span><span style="color:#56B6C2;"> =</span><span style="color:#ABB2BF;"> [</span><span style="color:#98C379;">&quot;2&quot;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&quot;3&quot;</span><span style="color:#ABB2BF;">];</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">([</span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">3</span><span style="color:#ABB2BF;">, ...</span><span style="color:#E06C75;">arr</span><span style="color:#ABB2BF;">]);</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><p>解构内部也是使用遍历器</p><div class="language-javascript line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">javascript</span><pre class="shiki one-dark-pro vp-code" style="background-color:#282c34;color:#abb2bf;" tabindex="0"><code><span class="line"><span style="color:#C678DD;">let</span><span style="color:#E06C75;"> hd</span><span style="color:#56B6C2;"> =</span><span style="color:#C678DD;"> new</span><span style="color:#61AFEF;"> Set</span><span style="color:#ABB2BF;">().</span><span style="color:#61AFEF;">add</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&quot;3&quot;</span><span style="color:#ABB2BF;">).</span><span style="color:#61AFEF;">add</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&quot;4&quot;</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#ABB2BF;">[</span><span style="color:#E06C75;">a</span><span style="color:#ABB2BF;">, </span><span style="color:#E06C75;">b</span><span style="color:#ABB2BF;">] </span><span style="color:#56B6C2;">=</span><span style="color:#E06C75;"> hd</span><span style="color:#ABB2BF;">;</span></span>
<span class="line"><span style="color:#E5C07B;">console</span><span style="color:#ABB2BF;">.</span><span style="color:#61AFEF;">log</span><span style="color:#ABB2BF;">(</span><span style="color:#E06C75;">a</span><span style="color:#ABB2BF;">, </span><span style="color:#E06C75;">b</span><span style="color:#ABB2BF;">); </span><span style="color:#7F848E;font-style:italic;">//3 4</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><h2 id="for-of" tabindex="-1">for/of <a class="header-anchor" href="#for-of" aria-label="Permalink to &quot;for/of&quot;">​</a></h2><p>拥有迭代特性即包含 <code>Symbol.iterator</code> 方法的数据结构，就可以使用<code>for/of</code> 遍历操作。</p></div></div></main><footer class="VPDocFooter" data-v-39a288b8 data-v-e257564d><!--[--><!--]--><div class="edit-info" data-v-e257564d><!----><div class="last-updated" data-v-e257564d><p class="VPLastUpdated" data-v-e257564d data-v-e98dd255>最后更新: <time datetime="2024-12-30T14:20:32.000Z" data-v-e98dd255></time></p></div></div><nav class="prev-next" aria-labelledby="doc-footer-aria-label" data-v-e257564d><span class="visually-hidden" id="doc-footer-aria-label" data-v-e257564d>Pager</span><div class="pager" data-v-e257564d><a class="VPLink link pager-link prev" href="/frontend/js%E5%9F%BA%E7%A1%80/%E7%B1%BB.html" data-v-e257564d><!--[--><span class="desc" data-v-e257564d>上一篇</span><span class="title" data-v-e257564d>类</span><!--]--></a></div><div class="pager" data-v-e257564d><!----></div></nav></footer><!--[--><!--]--></div></div></div><!--[--><!--]--></div></div><!----><!--[--><!--]--></div></div>
    
    
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